Transmission line protective system



Aug. 30, 1932. G LESCH 1,873,972

TRNSMISSION LINE PROTECTIVE SYSTEI Filed Dec. 10. 1929 Inventor Guntram Lesa/1 Atfomgl Patented Aug. 30, 1932 UNITED STATES PATENT OFFICE GUNTRAH LESCH, OF MANNHEIM-FREUDENHEIM, GERMANY, ASSIGNOR '10 AKTIEN- GESELLSGHAFT BROWN BOVERI & GIE., OF BADEN, SWITZERLAND, A. JOINT-STOCK COMPANY OF SWITZERLAN D TRANSMISSION LINE PROTECTIVE SYSTEM.

Application filed December 10, 1929, Serial No.

' This invention relates to protective systems for high voltage lines supplying current to a plurality of low voltage lines such as consumers lines.

n It is highly desirable to restrict a disturbhigh voltage circuit breaker upon the occurrence of a short circuit in one of the low voltage lines. The devices for operating the high voltage circuit breaker are usually of the quick-acting type to minimize the damage due to a short circuit in the high voltage line and the low voltage protective devices may have the same or a longer time delay period to operate but cannot be permitted to operate on a shorter time delay period than that of the high voltage circuit breaker itself. Disconnection of the high voltage circuit breaker upon the occurrence of a short circuit in one of the low voltage lines supplied thereby may, however, be prevented if means a are provided for preventing the operation of the high voltage circuit breaker releasing de vice upon the occurrence of a short circuit in one only of the low voltage lines.

It is, therefore, among the objects of the present invention to provide a protective system to prevent disturbance in a high voltage system supplying a plurality of low voltage or a consumers supply lines upon the occurrence of a short circuit in one of the low voltage lines.

Another object of the invention is to provide a system which will prevent disconnection of the high voltage line supplying a plurality of low voltage lines by preventing operation of a device for releasing a circuit breaker connecting the high voltage and the 7 low voltagelines.

Another object of the invention is to provide a protective system forhigh voltage lines supplying a plurality of low voltage lines in which an additional voltage is applied to the voltage coil of a relay controlling operatlon of the high voltage circuit breaker, upon the occurrence of a short circuit in a low voltage line, which voltage is dependent in amount 413,015, and in- Germany December 10, 1928.

and phase position on the short circuit current in the low voltage line while in case of a short circuit in the high voltage line the voltage coil of the circuit breaker releasing the relay is acted upon by a voltage proportional to that of the high voltage line.

Objects and advantages, other than those above set forth, will be apparent from the fol lowing description and the drawing which shows a diagrammatic representation of an embodiment of the invention illustrating a high voltage line supplying a group of low voltage lines.

Referring more particularly to the drawing by characters of reference, the reference numeral 1 indicates a high voltage line or bus bar connected to a low voltage line or bus bar 2 from which are taken a plurality of feeder or consumers lines 3 and 4, of which only 3 and at are shown. The high voltage line 1 and the low voltage line 2 are connected by a high voltage circuit breaker 6, a transformer 7 and a low voltage circuit breaker 8. The high voltage circuit breaker 6 is opened through the action of a circuit breaker releasing coil 9 supplied from a source of current 11 through the action of an armature 12 actuated by a voltage coil 13 and a current coil 14. The current coil 14 is supplied with current from a current transformer 16 connected into the line between the high voltage circuit breaker 6 and the transformer 7 and the voltage coil 13 is supplied from an auxiliary low voltage bus bar or line 17 which is connected with and supplied from the high voltage line 1 by the transformer 18. Impedances 21, 22 and 23, each of which may comprise a reactance or a resistance or both, are connected into the lines between the transformer 18 and the low voltage auxiliary bus bar 17. The impedances 21, 22 and 23 are connected in series with current transformers 26, 27 and 28, placed in the line between the transformer 7 and the low voltage circuit breaker 8.

Under the usual practise in arranging circuit breaker operating relays to protect lines of the above described character from the effects of excessive short circuits, a short circuit in the low voltage bus bar 2 causes a drop of voltage in the load transformer 7 so that 2 lama erated first thereby entirely disconnecting the ,7

low voltage rbusbar and cutting the service ofi from all of the low voltage feeders.

If the voltage in the voltage coil of the high voltage circuit breakenoperating relaycan be maintained upon the occurrence of a short circuit in the low voltage side,-the-high voltage circuit breaker Will not be operated and the service to the feedenlines, not affected by the short circuit, will not be cutofi. The present invention provides a circuit or system in which an additionalfvoltage is supplied to the voltage coil of the high voltagercircuit breaker operating relay to prevent such relay from operating to open the circuit breaker so that the slowerrelays (not shown) in the feeder line affected may operate to out off the afi'ected line. The high I voltagecircuit breaker operating relay is, accordingly, supplied by a voltage component dependent on the low voltage line short circuit current by the use'of impedances which keep the voltage above a value permitting operation of the high voltage circuit'breaker so that a sufiicient length of tlme 1's available to permit the slower low voltage circuit breaker relays to operate. a

l/Vhen a short circuit occurs in the low voltage feeder lines supplied from a'low voltage bus bar inthe system, accordingto the invention, the voltage in the auxiliary bus'bar 17 is maintained, by the impedances V .21, 22, and 23, at 'a value proportional to the current passing through the current transformers 26, 27 and 28 so that the voltage sup- Qplied from the auxiliary bus bar 17 to the voltage coil 13 of the high voltage circuit the value at which such relay Would cause operation of the high-voltage circuit-breaker 6. The present system accordinglypermits the afiected feeder or consumers line to be disconnected vvithout cutting off the high 1 voltage bus bar;

Although only a few embodiments'of this invention have been illustrated and described, it Will be understood that various =3 other embodiments are possible, and that various changes may be made Without departing from the spirit-of the invention or the scope of the appended claims.

. The invention claimed is:

1. In a protective system for high voltage said high voltage line for controlling the openingof said high voltage circuit breaker,

and meansfor supplying an additional voltage to said relay to prevent operation of said circuit breaker upon occurrence of a short circuit in one of the loW voltage lines, the additional voltage being 1 dependent in amount and phase position on the current in the short circuit in the loW voltage line.

2. Inca protective system for high voltage a transmission lines supplying a plurality of loW voltage lines, a high voltage circuit breaker, a relay for controlling the opening of said'c'ircuit breaker, said relay being operable by a voltageproportional to that of the high voltage lines upon occurrence'of a short circuit current therein, and means for supplying an additional voltage to said relay to prevent operation of "said circuit breaker upon occurrence of a short circuit'in one'of the low voltage lines.

3. In a protective system for high voltage transmission lines supplying a plurality of lov'vfvoltage lines, a high voltage circuit breaker, a relay supplied With potential from and operative in dependence upon the potent1al of the high voltage line for controlling" the opening of said circuit breaker, and means compr sing 1mpeda'nces for controlling the supply of an additional voltage to said relay in dependence on the current in 'a'short circuit in the low voltage lines, the additional voltage preventing operation offlsaid relay due to the lOW voltage line short circuit.

4. In a .protectivesystem for high voltage transmission lines supplying a plurality of low voltage lines, a high voltage circuit breaker, a relay having a voltage coil for controlling theopening .of said circuit breaker, a low voltage line for supplying voltage to said relay, impedances-connected :With said relay supply line, and current transformers connected with the low voltage lines and said lmpedance's' for controlling the voltage in Sa1d relay supply line in dependenceon'the v current in ashort circuit in one of the low breaker releasing relay is malntained above voltage lines to prevent operation of said circuit breaker. V

5. In a protective system for high voltage ment responsive lZOflOW of current in said high voltage line operative to cause said disconnection and an element responsive to flow of current in said low voltage lines operative to prevent said disconnection operation of the said circuit breaker upon occurrence of a Thort circuit in any one of said low voltage mes. V

In testimony whereof I havehereunto subscribed my name this 26th day of November A.;D. 1929.

"DRJGUNTRAM Lnsoni 

